This multicenter, prospective, observational study will evaluate the efficacy and safety of Pegasys (peginterferon alfa-2a) in routine clinical practice in patients with HBeAg-positive or HBeAg-negative chronic hepatitis B. Eligible patients receiving treatment with Pegasys according to standard of care and the summary od product characteristics/local labelling will be followed for the duration of treatment and up to 2 years of follow-up.